Torque responsive overload switch



'Jam. 21, 1969 c. R. BARNES 3,423,546

TORQUE RESPONSIVE OVERLOAD SWITCH Filed Dec. 29, 1966 United States Patent O 3,423,546 TORQUE RESPONSIVE OVERLOAD SWITCH Clyde R. Barnes, Ossian, Ind., assignor to Mix-Mill, Inc., Bluffton, Ind., a corporation of Indiana Filed Dec. 29, 1966, Ser. No. 605,710 US. Cl. 200-52 Int. Cl. H01h 35/06 2 Claims ABSTRACT OF THE DISCLOSURE A driving means drives a shaft on which it is rotatably mounted, through a pin of limited strength, suflicient to drive the shaft under normal loads. A switch is located near the shaft and an actuator for the switch is mounted on the shaft biased toward the switch held by the pin. Excessive resistance at the shaft causes the pin to yield, disabling the drive and permitting the biasing means to move the switch actuator axially sufliciently to actuate the motor disabling switch.

SUMMARY OF THE INVENTION BACKGROUND OF THE INVENTION The invention is intended for use in a farm feed preparation device which conveys various types of feed to a common grinder and mixes them together. Various conditions may cause excessive loads to be placed on the mechanism, such as the presence of foreign matter, the jamming of an auger conveyor, failure of lubrication, or the like. For protection of both the motor and the mechanism driven by the motor it is desirable that the torque be limited. Moreover, in this particular device, and many others, it is important that other devices stop when one is disabled. My novel overload switch both turns off the motor and disables the particular drive using a single mechanism. Having been tripped the mechanism cannot again be re-set without replacing the pin, discouraging an attempt to operate the mechanism before the source of excessive load has been found and corrected. At the same time the pin is readily replaced. The parts of the device are all inexpensive and readily manufactured, and give efficient and trouble free operation.

In the drawings:

FIG. 1 is an exploded View of the parts of my device.

FIG. 2 is a perspective view showing the parts assembled in operative relation.

FIG. 3 is an identical view showing the position of the parts after an overload has occurred.

DESCRIPTION The drawings show a shaft which is associated with a mechanism to be driven in one direction of rotation and which is to be protected. Shaft 10 may either be a part of the mechanism itself, or it may be provided with further drive means to drive such a mechanism. Shaft 10 is driven from motor 47 by belt 18 and a pulley 11, which is mounted to be freely rotatable on shaft 10 but is axially fixed with respect thereto by shaft collar Patented Jan. 21, 1969 17. Shaft 10 is provided with a bore 12 in which is a pin 13 extending radially a substantial distance at either side of the shaft 10. Pulley 11 is provided with drive members or projections 14 spaced apart.

An annular switch actuator disc 20 is rotatably mounted on extension 15 of shaft 10. Extension 15 may comprise a bolt received in a threaded bore 16 in the end of shaft 10. Disc 20 is on the other side of pin 13 from drive pulley 11, and is freely rotatable on shaft 10. Disc 20 is provided with axially extending retainers 21 to receive pin 13, the retainers 21 being each having a hook or slot 22 which is closed in the direction of rotation of pin 13, and open in the reverse direction. In the preferred form, the retainers 21 are also provided with a radially extending flange 23 spaced circumferentially in the direction of rotation from hook 22 of retainer 21, preferably formed from the same sheet of material. A spring 24 mounted on the shaft between the pin and the switch actuator provides a biasing force tending to keep the hooks 22 on retainer 21 in engagement with the pin 13 during normal operation (in conjunction with the slope of slots or hooks 22 from. the plane normal to shaft 10) and to move the actuator disc 20 into contact with the arm 31 of the switch 30 when an overload occurs thus opening the switch contacts in the motor circuit. Arm 31 is normally spaced 1, inch to inch from disc 20 as shown in FIG. 2.

In operation, the drive members 14 on the drive pulley 11 engage the pin 13 which is in the bore 12 in shaft 10 thus driving the shaft. If the resistance torque on shaft 10 is in excess of normal requirements, the pin 13 will bend, permitting the drive members 14 to strike the radial flanges 23. When pin 13 has been bent sufficiently, its ends will no longer extend radially far enough to engage the drive members 14 on the drive pulley, at which point the drive members drive solely against flanges 23 and will disengage the hook portions 22 of member 21, from the drive pin 13. The slot 22 which forms the hook is slightly inclined from the plane normal to shaft-10 so that the disengagement of the hook 22 from the pin 13 is agamst the bias of spring 24, This insures that the device will be stable in normal operation, since the biasing spring provides a force tending to keep the hook or slot 22 engaged with the pin 13. However, when the hook 22 is disengaged from the pin by circumferential movement of hookmember 21 with respect to the shaft 10, the biaslng spring 24 pushes actuator disc 20 axially to strike the arm 31 of overload protector switch 30 and turn oif the motor. At the same time, even if the motor should continue to run, the drive to shaft 10 is interrupted because pin 13 is bent too far to engage projections 21, this being the only driving connection between the pulley 11 and the shaft 10. Disc 20 is axially displaced, as described, and belng freely rotatable cannot drive the shaft in any case.

This structure is particularly useful where complete overload protection requires not only that drive to a shaft be interrupted, but also that other associated mechanisms be switched off. For instance, an interruption in service in one conveyor may require shutting off other conveyors before or after it in the system, or the disabling of devices receiving the output.

I claim:

1. In combination with a shaft, a driving means rotatably supported on the shaft, a motor operatively connected with said driving means, and an electric circuit adapted to control the operation of said motor, said circuit including a switch having normally closed contacts, said motor being adapted to drive said drive means in a single direction of rotation; the improvement comprising a combined torque-releasable driving connection and torque responsive switch actuator, including an axially extending drive member on said driving means and spaced radially from its axis, a bore through said shaft, a pin extending through said shaft and having an end extending into the path of said'drive member to turn said shaft with said drive member, said pin having only sufiicient lateral resistance to deflection at theradius of said drive member to transmit allowable driving forces to said shaft, a switch actuator mounted for axial and rotational movement respecting said shaft, biasing means biasing said switch actuator away from said pin and toward a position to actuate said switch, and securing means adapted to secure said switch actuator to said pin against said bias only while said'pin extends into the path of said drive member, said securing means comprising an axially extending portion of said switch actuator provided with a hook, said hook opening rearwardly of the direction of rotation of said actuator and being adapted to said pin to resist axial movement of said actuator, said axially extending portion of said securing means including a radially extending portion immediately adjacent the closed side of said hook and extending into the path of said drive member.

2. The device of claim 1 in which said hook is between said drive member and said shaft in its operating position, said. radial portion of said securing means being circumferentially spaced ahead of said projection on said driving member in the direction of rotation when said pin extends into the path of said driving member.

References Cited UNITED STATES PATENTS 2,022,007 11/1935 Moore. 2,037,260 4/ 1936 Nelson. 2,628,337 2/1953 Getz.

BERNARD A. GILHEANY, Primary Examiner.

F. E. BELL, Assistant Examiner. 

